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ABSTRACT: The prototype of PLS Linac klystron tube operating at 2856 MHz is under development by PAL. The self-design process for the klystron components are initiated with the results of the regeneration experience of failed klystron tubes at PLS Linac. The klystron components comprise of a thermionic electron gun, the segmented main accelerating cavity structures including RF input coupler and output voltage waveguide, a collector and two RF windows. The design utilizes a relatively proven technological approach for the klystron tubes currently in use, and the fabrication process using high precision machining and novel joining techniques are applied. The mechanical design considerations and manufacturing details of the PLS S-band klystron are presented.
Vacuum Electronics, 2003 4th IEEE International Conference on; 06/2003
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ABSTRACT: A 100-MeV high-intensity (20 mA CW) proton linac is being built in the KAERI (Korea Atomic Energy Research Institute), Korea. Beam diagnostic system for the machine require to include BCMs (Beam Current Monitors), BPPMs (Beam Position and Phase Monitors), and other devices. BCMs are of special importance for high-intensity proton linacs, since the control of beam loss is critical. They should have high stability and resolution better than 5E-4. BPPMs are for measuring beam position and phase (w.r.t RF) simultaneously, that are crucial for the successful commissioning and operation of the accelerator. All diagnostic devices are required to operate both in CW and pulsed (several ms) modes. Pulsed mode operation is useful when machine tuning and commissioning. In this article, we report the developmental status of beam diagnostic devices for the KOMAC accelerator, with detailed description on the BPPM PU design.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: The timing system for the Pohang Light Source (PLS) storage ring consists of a trigger synchronize module, a fine delay module, a repetition rate pulse generator module, and so on. All the timing modules are installed in the VXI crate and controlled by the 32 bit microprocessors with the host computer. Although the timing system has been operated without any serious problems since commissioning in 1994, there were some minor troubles, and the performances were not so excellent. Therefore, upgrade of the timing system is progressing with a synchronous universal counter and other commercial modules of NIM type for increasing of a reliability, easy maintenance, low timing jitters, and all types of beam filling pattern.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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I.H. Yu,
D.T. Kim,
J.S. Yang,
H.S. Kang,
W.H. Hwang,
M.H. Chun,
K.M. Ha,
Y.J. Han,
S.C. Kim, S.H. Nam,
J.M. Han,
H.J. Kwon,
Y.S. Cho,
K.T. Seol
[show abstract]
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ABSTRACT: At the 100 MeV proton linac of the KOMAC (Korea Multi-Purpose Accelerator Complex), the low level RF system provides field control for the entire KOMAC proton linac, including an RFQ and a DTL1 at 350 MHz as well as 7 DTL cavities at 700 MHz. In addition to field control, it provides cavity resonance control, and incorporates the personnel and machine protection functions. An accelerator electric field stability of ± 1% in amplitude and ± 1° in phase is required for the RF system. In order to accomplish these requirements, a digital feedback control technique is adopted for flexibility of the feedback and feed forward algorithm implementation. In this paper, the detailed description of the low level RF system is given.
Particle Accelerator Conference, 2003. PAC 2003. Proceedings of the; 06/2003
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ABSTRACT: Multi-channel seismic data acquired on the South Shetland margin, northern Antarctic Peninsula, show that Bottom Simulating Reflectors (BSRs) are widespread in the area, implying large volumes of gas hydrates. In order to estimate the volume of gas hydrate in the area, interval velocities were determined using a 1-D velocity inversion method and porosities were deduced from their relationship with sub-bottom depth for terrigenous sediments. Because data such as well logs are not available, we made two baseline models for the velocities and porosities of non-gas hydrate-bearing sediments in the area, considering the velocity jump observed at the shallow sub-bottom depth due to joint contributions of gas hydrate and a shallow unconformity. The difference between the results of the two models is not significant. The parameters used to estimate the total volume of gas hydrate in the study area were 145 km of total length of BSRs identified on seismic profiles, 350 m thickness and 15 km width of gas hydrate-bearing sediments, and 6.3% of the average volume gas hydrate concentration (based on the second baseline model). Assuming that gas hydrates exist only where BSRs are observed, the total volume of gas hydrates along the seismic profiles in the area is about 4.8 × 1010 m3 (7.7 × 1012 m3 volume of methane at standard temperature and pressure).
Antarctic Science 05/2003; 15(02):271 - 282. · 1.56 Impact Factor
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ABSTRACT: Summary form only given, as follows. In designing a compact and high efficiency TWT microwave amplifier, the role of a high power density DC power supply is very important. In order to reduce volume of the power supply, it is necessary to increase switching frequency of the power supply. The high operation frequency mainly reduces transformer volume in the power supply. However, a step-up ratio of the transformer in the high voltage DC power supply needs to be maintained. Therefore, the pulse transformer should be carefully designed to fulfill its function in the power supply. A high frequency and high voltage pulse transformer is designed, fabricated, and tested. Switching frequency of the transformer is 100 kHz. Input and output voltages of the transformer are 250 V and 4 kV, respectively. Normal operation power of the transformer is 3.3 kW. Maximum volume of the transformer is 400cm<sup>3 </sup>. The transformer will be installed in a metal box that has nominal operation temperature of 85 degree centigrade. The transformer and other high voltage components in the box will be molded with Silicon RIV that has a very low thermal conductivity. Procedure of design and test results will be presented. Results of various parameters such as transformer loss, temperature rise, leakage inductance, distributed capacitance, and hysteresis characteristics will be discussed in detail. In addition, thermal analysis results from ANSYS code for three different operation conditions will be discussed
Pulsed Power Plasma Science, 2001. IEEE Conference Record - Abstracts; 02/2001
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ABSTRACT: From the year 2000, the PLS storage ring stores 2.5 GeV
high-energy electron beam by raising the energy from the 2.0 GeV
injection energy. The stored current is presently 180 mA, which is
limited by the available RF energy at 2.5 GeV. In May 2000, we succeeded
in storing 300 mA at 2.0 GeV achieving the last design goal of PLS.
Further, the new record of the maximum beam current, 450 mA, was made in
April 2001. At present, PLS has 13 beamlines in operation, 1 beamline
under commissioning and 6 beamlines under construction. Other progresses
and issues of the PLS operation will be discussed further
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: Waveguide valves capable of handling a peak power of 80 MW are
required at the time of klystron replacement in PLS Linac. We designed a
U-shaped waveguide valve and made two prototypes. However, they have
some problems caused by RF power leak from the waveguide to the vacuum
enclosure. This caused an increase of vacuum pressure and arcing in the
vacuum chamber at the power level of 60 MW. A new choke flange has been
designed with MAFIA code to solve problems caused by the RF power leak.
A model choke flange has been fabricated and tested with a Network
Analyzer and a 600 W solid state amplifier. It was observed that the RF
leak at the choke flange can be reduced more than 20 dB in comparison
with no choke case. High power RF test for the new waveguide valve with
RF choke flange was performed in S-band resonant ring. The RF
transmission through the valve was achieved up to 125 MW peak power
level at the pulse width of 4 μs and the repetition rate of 30 Hz
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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E.-S. Kim,
M.-H. Chun,
J.-Y. Huang,
U.-H. Huang,
H.-S. Kang,
D.-T. Kim, S.-H. Nam,
H.-J. Park,
J.-S. Yang,
M. Yoon,
I.-H. Yu
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ABSTRACT: We present investigations on beam instabilities that have been
observed at 2.0 GeV and 2.5 GeV in the PLS storage ring. Stored beam
currents of 2.0 GeV in the ring has been mainly limited by coupled-bunch
instabilities. We have investigated dependences of the coupled-bunch
instabilities on betatron tune, chromaticity and RF cavity temperatures
at 2.0 GeV. 450 mA beam could be stored at 2.0 GeV. Bunch filling
patterns and betatron tune are investigated to suppress the beam
instabilities at 2.5 GeV. At 2.5 GeV, we do not observe any beam
instabilities up to 200 mA. Higher beam currents than 200 mA are limited
by total RF power
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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Yujong Kim,
C. Kim,
K.H. Kim,
C.D. Park,
M.H. Chun,
J.S. Yang,
I.H. Yu,
M. Kwon,
J.Y. Huang, S.H. Nam,
M.H. Cho,
W. Namkung,
I.S. Ko
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ABSTRACT: In the Pohang Light Source storage ring, we empty 68 buckets of
total 468 buckets to cure the conventional ion trapping. However, the
fast beam-ion instability is occasionally generated at higher beam
current. Immediately after the strong vertical beam shaking due to the
fast beam-ion instability, the longitudinal coupled bunch mode
instabilities are substantially damped down without any active feedback
system. We have described the fast beam-ion instability driven
longitudinal damping and its mechanism in the Pohang Light Source
storage ring
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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Yujong Kim,
C. Kim,
K.H. Kim,
J.S. Yang,
M.H. Chun,
I.H. Yu,
M. Kwon,
J.Y. Huang, S.H. Nam,
M.H. Cho,
W. Namkung,
I.S. Ko
[show abstract]
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ABSTRACT: During the normal operation period in the Pohang Light Source
(PLS) storage ring, the spontaneous bunch length oscillation or beating
is generated by the nonlinear effects of the RF noise whose frequency is
much lower than the bifurcation frequency. Due to the bunch length
beating, we can not supply the uniform intensity beams to users. We have
described the observed bunch length beating and its mechanism in the PLS
storage ring with a simulation
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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Yujong Kim,
C. Kim,
K.H. Kim,
M.H. Chun,
J.S. Yang,
I.H. Yu,
M. Kwon,
J.Y. Huang, S.H. Nam,
M.H. Cho,
W. Namkung,
I.S. Ko
[show abstract]
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ABSTRACT: From the recent data analysis of the longitudinal feedback system
and the streak camera, we have found a longitudinal relaxation beam
oscillation whose frequency is a multiple of 36 Hz. When the relaxation
oscillation is generated, horizontally oscillating wide beams are
observed at the diagnostic beamline, and the beam lifetime is
fluctuated. The strength of the longitudinal coupled bunch mode
instabilities is also modulated sinusoidally. We have described the
observed longitudinal relaxation oscillation in the Pohang Light Source
storage ring
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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Yujong Kim,
C. Kim,
K.H. Kim,
I.H. Yu,
J.S. Yang,
M.H. Chun,
M. Kwon,
J.Y. Huang, S.H. Nam,
M.H. Cho,
W. Namkung,
I.S. Ko
[show abstract]
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ABSTRACT: In the Pohang Light Source (PLS) storage ring, we have
occasionally experienced the abnormal spontaneous beam. lifetime
reduction and strong longitudinal damping. Due to the abnormal beam
lifetime reduction, available beam time is reduced substantially. From
the recent data analysis of the PLS longitudinal feedback system (LFS)
and the streak camera, we have found that the abnormal phenomena can be
generated by the RF noise via the dipole mode parametric resonance of
the RF phase modulation. We describe the observation of the dipole mode
parametric resonance driven by the RF noise and compare it with a
simulation result in the PLS storage ring
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: A triggered multi-gap pseudo-spark discharge system (TPDS) is designed and fabricated. The TPDS has ten gaps. The TPDS has been operated up to 35 kV at 60 mTorr of Ar gas. The peak beam current extracted from the anode electrode is measured as a function of external capacitance. The external capacitance is varied from 1 nF to 10 nF. The maximum peak beam current is obtained with 1 nF external capacitance. A typical pulse duration of the electron beam is 30 ns. The density of the electron beam is also investigated by using a spectroscopic measurement. The principle of space charge neutralization is adopted for the electron beam density analysis. The measured value of the electron beam density is about 2.5×10<sup>16</sup> cm<sup>-3</sup> with an experimental condition of 1 nF external capacitance, 35 kV charging voltage, and 60 mTorr of He gas.
Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers; 02/2001
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[show abstract]
[hide abstract]
ABSTRACT: With the installation of the first insertion device U7 and more
and more sophisticated experiments in the Pohang Light Source (PLS), the
synchrotron radiation users now demand more accurate measurement and
control of the closed orbit. As the essential part of the accurate orbit
measurement and feedback, all the BPM electronics and data acquisition
system have been upgraded. In the new BPM system, we adopted a
commercial BPM processor, which has better than 5 μm accuracy over 65
dB dynamic range of input signal. The data acquisition board is made
in-house utilizing a fast ADC and an on-board microprocessor. New BPMs
and various machine diagnostics on the orbit drift with the aid of new
BPMs will be described in this paper
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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ABSTRACT: The Pohang Light Source (PLS) storage ring uses two bunch-by-bunch
feedback systems - a longitudinal feedback system (LFS) and a transverse
feedback system (TFS) - to cure the coupled bunch instabilities due to
higher order modes of RF cavities and resistive wall impedance. The LFS
employs the digital electronics developed for ALS and PEPII and uses a
cavity-type kicker, and it was successfully commissioned in 1999 with
the aid of SLAC. The TFS uses analog two-tap coaxial notch filters for
the closed orbit offset signal rejection. The TFS is now in upgrade to
use one kicker per transverse plane to improve efficiency over the
previous system with a kicker combining both planes in a single
structure. This paper will describe the achieved results of curing the
coupled bunch instabilities by using the LFS and TFS together with
current status
Particle Accelerator Conference, 2001. PAC 2001. Proceedings of the 2001; 02/2001
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[show abstract]
[hide abstract]
ABSTRACT: In designing a compact and high efficiency TWT microwave amplifier, the role of a high power density DC power supply is very important. In order to reduce volume of the power supply, it is necessary to increase switching frequency of the power supply. The high operation frequency mainly reduces transformer volume in the power supply. However, a step-up ratio of the transformer in the high voltage DC power supply needs to be maintained. Therefore, the pulse transformer should be carefully designed to fulfil its function in the power supply. A high frequency and high voltage pulse transformer is designed, fabricated, and tested. Switching frequency of the transformer is 100 kHz. Input and output voltages of the transformer are 250 V and 4 kV, respectively. Normal operation power of the transformer is 3 kW. Maximum volume of the transformer is 400 cm<sup>3</sup>. The power density is thus 7.5 W/cm<sup>3</sup>. The transformer will be installed in a metal box that has nominal operation temperature of 85 degree centigrade. The transformer and other high voltage components in the box will be molded with silicon RIV that has a very low thermal conductivity. Procedures of design and test results are discussed. Analytical as well as experimental results of various parameters such as transformer loss, temperature rise, leakage inductance, and distributed capacitance are also discussed. In addition, thermal analysis results from ANSYS code for three different operation conditions are discussed.
Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers; 02/2001
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ABSTRACT: The purpose of this experiment is to improve understanding of the high current vacuum arc phenomena in a triggered vacuum switch (TVS). The TVS used in the experiment has a rod array electrode. The cross section of each rod has trapezoidal shape. A spectroscopic measurement was performed up to 150 kA peak current at the center of electrodes. The tested electrode material was Fe. Measured Fe spectrum range was from 200 nm to 900 nm. Measurement result showed that over 90 percent of the charge states were Fe II, and the others were Fe I and Fe III. By assuming a local thermal equilibrium (LTE), electron temperatures of the TVS arc were determined from the relative line intensity ratio of Fe II. The electron temperatures at the center of electrodes were measured as 1.5 eV and 2.5 eV with 26 kA and 64 kA peak currents, respectively. The electron temperature increased with its peak current.
Pulsed Power Plasma Science, 2001. PPPS-2001. Digest of Technical Papers; 02/2001
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ABSTRACT: The 2.0-GeV Pohang light source (PLS) is a third-generation
synchrotron light source that is the first such facility in Korea and
the fifth in the world. The PLS mainly consisted of a full-energy
injection linac and a storage ring. Four kicker magnets are installed in
the storage ring tunnel to move the stored beam orbit in the storage
ring closer to the injected beam from the beam transfer line. The
injected beam then falls into the storage ring beam dynamic aperture. A
kicker magnet modulator drives all four kicker magnets to maintain field
balance and synchronized kick of the beam. Specification of the kicker
magnet modulator is ~6.0-μs-full width, 200-ns flattop width with
±0.2% regulation, ~24-kA peak current, and 10-Hz repetition rate.
Two thyratron switches (EEV CX-1536AX) are used in the system. As the
inverse voltage is dangerous to thyratron operation, a new surge
suppression circuit was developed. The kicker modulator has been
operated very reliably since its installation in August 1995. In this
article, design, simulation, and experimental results of the kicker
magnet modulator are discussed. In addition, measurement result of
spatial B-field distribution in the kicker magnet and maximum operating
range of kicker magnet are discussed
IEEE Transactions on Plasma Science 11/2000; · 1.17 Impact Factor
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ABSTRACT: A thyratron is a very common switching device in many high-power
pulse systems. However, it is difficult to diagnose switching
characteristics of the thyratron during its operation. A new diagnostic
factor of the thyratron has been developed from a convection heat
transfer theory. The new diagnostic factor is obtained from a dependence
of a thyratron heater current on a thyratron internal gas pressure. We
have verified theoretical proprieties of the diagnostic factor and
confirmed experimentally that the assumption used in the theory is
applicable to typical thyratrons. Using the diagnostic factor, we have
designed and constructed an autoranging and autodiagnostic device for
the thyratron
IEEE Transactions on Plasma Science 11/2000; · 1.17 Impact Factor
